Accidental Fusion
by EveeFan
Summary: When a young Boss Monster finds a dead human, she doesn't know what to do. The moment she touches them, she wakes up in a body only slightly similar to her own. And it doesn't help when an equally confused voice appears in her own mind, desperate to return to her own. Note: This occurs in an AU where an OC replaces Frisk and Toriel had a second child, no other major differences.
1. Chapter 1

I walked through the Ruins. I regretted running away just because my mom's personality had clashed with mine. I now noticed a few things- primarily that she no longer checked for humans every day. I looked down at my furry, pale-blue hands- no idea where the blue came from. I had been hiding out in parts of the sprawling cave system for a long time.

And then I saw it.

There was a girl- a human girl- lying on the floor. She was rather beat-up and didn't seem to be living. I should have known better than to approach the collapsed girl with a teal glow starting to flow like a heavy gas, or like ink in water, from her chest. As I approached, what I had thought was blue blood started to pulse with light and then vanished. I panicked, and ran towards the body, tripping over my own feet.

I kneeled next to it. There were no signs that she was, or ever had been, alive. I filled with sorrow. If I hadn't run away, this could've been prevented. My mom would've seen her and taken her in. Even though I felt painful surges of what I had thought was sympathy rushing though me, I leaned down and put my hands on her chest. She could've been breathing really shallowly. But as soon as I had touched her, I blacked out.

I woke what could've been five minutes or years later. I was in the same room and there were no signs of dilapidation- or even anyone noticing me- so my guess was on the low side of that. My vision was tinted ever-so-slightly aquamarine, but I dismissed it as an aftereffect of the likely head impact from when I fell. I noticed that the girl's body had gone pale and the glow had vanished, but I just pictured that as her having been dead for a bit longer. I only started to get confused when I got up and was, although able to breathe, able to move almost as if I was wading through water that was up to my neck.

Not only was I swaying as if pushed by currents and trudging slowly with an unexpected amount of fluid friction from the air, but when I jumped, I could float.

I looked down at my hands- they glowed teal. I felt my head, where the hair on my scalp had grown at least half an inch. The tattered purple robe that had been my only possession ever since I ran away had vanished, replaced with a flowing, floor-skirting teal gown. I took another step forward, and saw as a slim foot -within a formal-looking violet shoe- much unlike my fuzzy bare ones- pushed beyond the boundary of the cloth that covered me.

It didn't help my worry when a voice that was much prettier than what mine has been described as to me issued from my mouth when I cried quietly for help. And then a thought passed through my mind in that same voice, not a thought of my own- "Where am I?"


	2. Chapter 2

I nearly fell on my knees when I heard that, but I was caught by the supernatural low-gravity field that seemed to apply only to me. When I caught myself in a pushup to spring back up, I noticed that I was at least a full foot taller than I had been earlier. My mouth flapped uselessly for a minute before I could finally muster the... I don't know, courage, I guess... to eject the words "Who's there?"

The fearful tones of the voice that echoed through my mind were silent for a moment, but then surprised me so much that I jumped- a few feet, actually, when you consider that I was in low gravity- when it quietly murmured "I... I'm Elysa... But who are you?" I started to relax a bit. No awkward conversation starts. You can't exactly just go up to a HUMAN SOUL WHOSE CONCIOUSNESS HAS TAKEN UP RESIDENCE IN YOUR MIND and say (think?) "So, beautiful weather we're having, eh?"

I started to speak out loud, but then stuttered and went into a very deep thought. _My name is Siarel..._ I didn't hear her response for a moment, and just as I was about to repeat that out loud, a voice said "nice."

I just sat there and blinked about a thousand million times. And then she asked me to stop blinking, since she was seeing through my eyes and it obstructed her vision. I asked her what to do next.

"Uh... Get me out of here."

Unbeknownst to me, as I began to enter contemplation of possible ways to expel her soul, I started to slowly float upward. And then it hit me. Both the best answer I could think of at the time, and the ceiling. _We should consult the royal scientist, Alphys. But to do that, we'll need to get through the Ruins..._ I winced internally, knowing that that meant I'd have to pass through my old home.

I (We?) wandered down the endless corridors that formed a maze. With my mom being the caretaker of the Ruins, I knew all the puzzles and mazes. We had started at the very beginning, the single-exited passageway that had been the starting place of the many humans I had mournfully greeted, remembering my late brother and his best friend.

I got lots of sideways looks, but nobody actually came up to me. I mean, the poor Froggits were terrified of my mom. What kind of intimidation did I unintentionally radiate? I eventually saw the blackened, still-leafy tree that marked the entrance to my home. I saw my mom tending flowers out in the front. She turned around and saw me. She started to yell "WHO ON EARTH ARE YOU AND-" but then she looked me in the eyes. I knew at that point that she recognized me. And it looked like the hardened look on her face just melted away into one of sadness.

"Why..." She looked at me as if she was looking at her pet dog that had just eaten her baby, or vice versa. It took me a moment to realize that she recognized that I had fused with a soul. _What do I say now?_ And the echo in my head suggested that I "Tell the truth- that I missed the soft flowers and died in the fall." I explained to my mom that I hadn't done anything, and a twinge of relief brought up the corners of her mouth. She invited me in, but I explained that I had to see Alphys- and soon- to un-fuse before the human soul was fully absorbed by mine, or, even worse, just died out.

She gave me a pie, which I ate (accompanied by the cheers of Elsya to "keep eating more of this delicious food!") before I headed out. I waved at Toriel with a smile, knowing I would see her again, and stepped out of the Ruins for the first time since before Asr- My brother (it only makes the sadness worse to use their name) died.


	3. Chapter 3

**A/N**

 **Wow. This chapter is really taking a long time. I'm at that point where I know what I want to do, but have no clue how. Prepare yourself for waits this long or longer, constantly, if you try to follow this fan fiction. I feel like I should do a "previously on Accidental Fusion" just because of the wait, but I won't. Well, I don't really have anything else to say in this note, but just if you have any confusions go ahead and pm me or review, I'll try and answer them.**

 **END A/N**

A blast of cold air hit the moment I stepped out of the door. There was snow falling from the "sky"… well, the top of the cave. At this point, I had WAY more on my mind than how the top end of the cave mimicked the top end of the surface. Elysa was silent. I started to walk on. The silence was too much for me. I decided I was going to clear up one of my more shallow confusions.

 _Uh… Elysa? What's it like in there?_

I cringed the moment I had thought it. I was worried that I might've somehow offended her. And she remained silent for a moment. But then I heard her start to… well… uh... talk? Think? I don't really know. But she started to explain.

"It's like there's this huge, panoramic view of what you can see. And if I look away from it… Below it, there's a grey, upside-down heart-shape with the number 20 beneath it. I don't know what that means. And above it there's a teal heart shape with the number 20 above it. And to either side, there's a little square-shaped area where everything you hear is transcribed, and an area where everything you think is. I honestly don't get any of it. Outside of that, it's all black. And when I look down at myself, it's just a white silhouette that resembles me."

I tried to picture myself in the same position. Before I could solidly see my own vision as only a fraction of what I saw, I bumped into something.

Bars.

I panicked for a moment. Who would set bars here? _WHY_ would they put bars here? Especially bars that, after sliding a few feet to the side, I could literally walk through with my arms spread and not touch? I thought I heard someone laugh behind me, but when I turned around, they were gone. And then I looked back in front of me. And there they were.

"WHA!" I leapt backward so powerfully that I had literally leapt over the bars, a feat that I could only accomplish with the help of my own personal low-grav field. Once I had landed, I realized how ridiculous the situation was. I had just leapt away like my life had depended on it from a slightly short skeleton in what appeared to be some form of hoodie. I completely forgave them for breaking out in laughter.

 **A/N**

 **Well, I have something now. I don't expect to be done with the next chapter for a while, or I could rush it, but then it would appear as a trollfic. So, if you have questions, you can review them and I might cover them in a note later, or just PM me.**

 **END A/N**


End file.
